1. Field Of The Invention
The present invention relates to improved wax compositions and fibrous substrates coated therewith, and more particularly to compositions of recrystallized heavy intermediate petroleum wax and polymeric hydrocarbon compounds. In addition, the wax compositions contain a tackifier resin and a phenolic anti-oxidant. These wax compositions are particularly suitable for coating fibrous substrates. The copending application of Richard L. Jones entitled "Fibrous Substrates Containing Hot Melt Coating Made From A Novel Petroleum Wax", Serial No. 07/278,700, Filed Nov. 30, 1988, describes fibrous substrates and a process for coating said substrates using the wax compositions disclosed herein, the disclosure of which is incorporated herein by reference.
It is known to coat fibrous substrates, for example, paper and the like with wax and wax like compositions. These coatings are particularly useful in preventing the migration of moisture either out or into a container treated therewith. Numerous waxes have been used as coatings for fibrous substrates in the past, including animal and vegetable waxes, for example, bees wax, wool wax, cotton wax and the like.
The mineral waxes, in particular, the petroleum waxes such as paraffin wax, microcrystalline waxes and the like are more commonly used at the present time to coat fibrous substrates. Blends of these waxes have additionally been used in the past. These wax coatings generally exhibit one or more deficiencies, such as, lack of sufficient hardness, scuff resistance, tensile strength, resistance to cracking, an opaque color and other undesirable characteristics. In the absence of microcrystalline waxes, distillate waxes are usually too brittle to be effective as coating waxes, particularly at ambient temperatures such as room temperature and below. To overcome these and other difficulties it has become common practice to use blends of certain additives in wax compositions. The use of polymers as additives in waxes has greatly improved certain characteristics in wax coatings, however, many wax coatings which use these additives still suffer from one or more disadvantages such as an opaque color, poor resistance to moisture, as well as insufficient heat and thermal stability, grease resistance and gloss stability. The wax compositions herein overcome these difficulties and, in addition, when applied as a coating to fibrous substrates are clear in color. This is important because it allows for writing and marks on the fibrous substrate to be visible to the eye after the coating is applied.
2. Description Of The Prior Art
Wax compositions, paper products containing coating of wax compositions and processes for making and producing the same are known and are currently practiced commercially.
For example, U. S. Pat. 2,999,828, issued Sept. 12, 1961, relates to wax compositions and sheet materials coated therewith. In particular, the patent discloses compositions of petroleum wax and polyethylene as a coating for sheet materials. The petroleum waxes used are of an intermediate class midway in molecular weight between paraffin wax and microcrystalline wax.
U.S. Pat. 3,025,167, issued Mar. 13, 1962, discloses a thermoplastic composition suitable for use as a coating on a flexible base sheet, such as paper. The thermoplastic composition consists of a petroleum wax having a melting point between 130.degree. F. and 170.degree. F. and an ethylene/vinyl acetate copolymer.
U.S. Pat. 3,192,062, issued June 29, 1965, relates to wax compositions and sheet materials coated therewith. The wax composition consists of a modified heavy distillate wax and a polyethylene compound or copolymers of ethylene with higher monoolefins or polypropylenes.
U.S. Pat. 3,272,690, issued Sept. 13, 1966, relates to a method of improving the wet strength of paper. The method involves blending a wax/ethylene vinyl acetate copolymer with paper pulp to impart an improved wet strength to fibrous materials. The wax employed in the blend is a paraffin crystalline wax.
U.S. Pat. 3,326,835, issued June 20, 1967, discloses petroleum wax compositions which are described as suitable for use in forming protective coatings for wrapping paper and paper board. The petroleum wax compositions consist of intermediate and microcrystalline waxes which have been upgraded by adding therewith a polybutene-1 resin.
U.S. Pat. 3,362,839, issued Jan. 9, 1968, relates to wax-containing compositions which are described as suitable for coating paper, cardboard, cartons and the like. The wax-containing compositions consist of blends of paraffin wax and microcrystalline wax and ester selected from vinyl acetate or ethyl acrylate and an N-substituted alkyl amide.
U.S. Pat. 3,440,194, issued April 22, 1969, discloses coating compositions consisting of petroleum wax, an interpolymer selected from the group of ethylene and vinyl acetate or ethylene and ethyl acrylate, or graft copolymers of polyethylene and dicarboxylic acid or anhydride thereof.
It must be noted, however, that the wax compositions comprising a recrystallized heavy intermediate wax and a polymeric hydrocarbon compound and/or in combination with a tackifier resin and phenolic anti-oxidant claimed herein are new and unappreciated by the prior art.